Polyvinyl alcohol cord tires

ABSTRACT

Polyvinyl alcohol fibers are provided containing boric acid or a borate salt thereof in an amount of 0.2 to 0.9 percent by weight of polyvinyl alcohol wherein the yarn tenacity of 120*C., the yarn initial modulus at 120*C. and the yarn creep at 135*C. are at least 7.5 g/d, 100 g/d and less than 2 percent, respectively. Radialply and belted bias ply tires are also provided which utilize said fibers in the cord of the breaker or belt, the fiber being twisted under a twist constant of ply of 800 to 1,300 and a cable twist (turns/10cm) of 80 to 100 percent of the ply twist (turns/10cm).

United States Patent [191 Tanaka et al.

[111 3,826,298 [451 July 30,1974

1 1 POLYVINYL ALCOHOL CORD TIRES [22] Filed: Jan. 5, 1972 [21] Appl. No.: 215,621

Related US. Application Data [63] Continuation-in-part of Ser. No. 90,816, Nov. 10,

[30] Foreign Application Priority Data Nov. 25, 1969 Japan 44-94790 Apr. 30, 1970 Japan 45-37354 [52] US. Cl. 152/359, 57/140 R [51] Int. Cl D02g 3/48, D02g 3/02 [58] Field of Search 57/139, 140 R, 140 BY;

[56] References Cited UNITED STATES PATENTS 2,058,778 10/1936 Dinsmore 57/140R 2,249,039 7/1941 Platt 57/140 R X 2,716,049 8/ 1955 Latour 3,007,228 1 H1961 Matsubuyashi 3,616,165 10/1971 Nishi 57/140 C X Primary Examiner-Donald E. Watkins Attorney, Agent, or Firm-Kaufman & Kramer 5 7] ABSTRACT Polyvinyl alcohol fibers are provided containing boric acid or a borate salt thereof in an amount of 0.2 to 0.9 percent by weight of polyvinyl alcohol wherein the yarn tenacity of 120C., the yarn initial modulus at 120C. and the yarn creep at 135C. are at least 7.5 g/d, 100 g/d and less than 2 percent, respectively. Radialply and belted bias ply tires are also provided which utilize said fibers in the cord of the breaker or belt, the fiber being twisted under a twist constant of ply of 800 to 1,300 and a cable twist (turns/10cm) of 80 to 100 percent of the ply twist (turns/10cm).

3 Claims, No Drawings 1 POLYVINYL ALCOHOL CORD TIRES This application is a continuation-in-part of copending application Ser. No. 90,816 filed Nov. 10, 1970.

The present invention relates to polyvinyl alcohol fibers which exhibit excellent properties at high temperature such as yarn tenacity, yarn initial modulus and yarn creep; it also relates to radial-ply and belted biasply tires which utilize said fibers in the cord of the breaker or belt,by twisting the same under predetermined twisting conditions.

Generally, polyvinyl alcohol (PVA) fibers surpass other synthetic fibers in breaking strength and initial modulus, and have recently found wide use in many fields, for instance, fiber reinforced plastics (FRP). It is a well-known fact that PVA fibers which are drawn to the drawable limit and minimized in heat-shrinkage exhibit outstanding breaking strength and initial modulus. However, PVA fibers, like many other synthetic fibers, undergo a deterioration in properties at high temperature in proportion to the rise in the temperature.

The primary object of the present invention is to obviate the above deficiencies in synthetic fibers by providing a PVA fiber having excellent properties at high temperature. It is another object of the present invention to provide radial-ply tires which employ said fiber in the cord of the breaker. It is still another object of the present invention to provide belted bias-ply tires which employ said fibers in the cord of the belt. More particularly, the synthetic fibers produced in accordance with the present invention are superior to conventional PVA fibers with respect to yarn tenacity, yarn initial modulus and yarn creep. The radial-ply or belted bias-ply tires which utilize the PVA fibers of the present invention in the cord of the breaker or belt give excellent results in the plunger test, high speed test, cornering power test, tread wear-resistance test and durability test, as will be seen hereinafter.

The PVA synthetic fibers of the present invention exhibit high crystallinity and molecular orientation, and are characterized by the high temperature properties indicated below and by the amount of boric acid (H 80 or a borate salt thereof contained therein,the

properties at high temperature being as follows:

yarn tenacity at 120C. at least 7.5 g/d yarn initial modulus at at least 100 g/d 120C.

am cree at 135C. less than 2% boric aci or borate salt 0.2 to 0.9% by weight of PVA content Generally speaking, the extensibility of synthetic fibers increases in proportion to the rise in temperature, and the strength and yarn initial modulus decrease. It can be easily speculated that this phenomenon occurs because movement is initiated in the molecular chain of the fiber in regions of low molecular orientation upon heating the fiber. This movement is soon transmitted to regions of the fiber where molecular orientation is intense. It is therefore important in the imporvement of the properties at high temperature of a synthetic fiber to surpress the movement of molecular chains as much as possible. This can be achieved either by (l) intensifying the orientation of the molecular chains to such an extent as to prevent them from moving, or (2) adding to the polymer a material which hinders the movement of molecular chains. These two remedies, however, when separately employed are not capable of achieveing the objects of the present invention, i.e., property improvement at high temperature such as improvement in yarn tenacity, yarn initial modulus and yarn creep. For instance, improvement in yarn initial modulus may be expected in a method wherein a conventional PVA fiber is subjected to post-treatment with boric acid; however, the same process will also result in a remarkable decrease in yarn tenacity.

It has been found in accordance with the present invention that the essential factor which fulfills the primary object of the present invention is a fibrous structure wherein the orientation of the molecular chains is quite intense as a whole but which contains a substance to prohibit the movement of the molecular chains where the molecular orientation is relatively loose. That is, a portion or all of the boric acid or borate salt thereof contained in the fiber may conbine with the PVA in relatively loose orientation, to prohibit the movement of the molecular chains caused by heating. When the amount of boric acid or borate salt does not measure up to 0.2% by weight of PVA, it is insufficient to restrain the chain movement. When the boric acid or borate salt content exceeds 0.9%, it will prevent the molecular chains from being highly oriented, thereby causing reduction of the yarn strength.

The PVA fibers of the present invention can be produced by a process comprising: preparing an aqueous solution of PVA which contains boric acid or borate (the spinning solution); spinning in a coagulating bath comprising a major amount of water, sodium hydroxide or potassium hydroxide and sodium sulfate, said materials being present in the coagulating bath in a predetermined amount; drawing the resulting fibers between rollers; neutralizing any alkali adhered to the fibers with acid; wet-heat drawing of the fibers; water-rinsing to adjust the amount of boric acid remaining in the fiber to be within a predetermined range; dehydrating and drying; and, dry-heat drawing.

The concentration of the coagulating bath, which has heretofore been used in the conventional wet spinning method to produce PVA fibers containing no boric acid or borate, is almost saturated with sodium sulfate, when sodium sulfate is used as the dehydrating salt in the bath. This is done because the fibers will stick to one another clue to insufficient coagulation, when the concentration of the dehydrating salt in said bath is lower than 300 g/l. Accordingly, the coagulating bath used in the present invention is further combined with sodium hydroxide or potassium hydroxide in a predetermined amount, thereby facilitating the spinning of spinning solutions containing boric acid or borate. The properties of the PVA fiber thus produced depend very little on the temperature. It is often observed that when the content of sodium sulfate is high in the coagulating bath, the drawability of the product tends to decrease. The PVA synthetic fibers produced in accordance with the present invention exhibit superior drawability and less temperature dependency as compared with conventional PVA fibers which contain no boric acid.

In accordance with the present invention, it has been found that the aqueous spinning solution of PVA containing boric acid or a borate salt thereof can be coagulated to produce PVA synthetic fibers having yarn tenacity, yarn initial modulus and yarn creep which hardly depend on the temperature. The method of the g present invention comprises spinning an aqueous solution of PVA containing boric acid or a borate salt thereof into a coagulating bath being kept strongly alkaline by the addition of to 100 g/l sodium hydroxide or potassium hydroxide and 100 to 330 g/l sodium sulfate, which is then subjected to subsequent treatments such as roller drawing, alkali neutralization, water-rinsing to adjust the residue of boric acid in the fiber to a range of 0.2 to 0.9 percent by weight of PVA, dehydration and drying, and dry-heat drawing.

It is preferable to add boric acid or a borate salt thereof to the spinning solution in an amount ranging between 1 and 5% by weight of PVA.

Boric acid or any borate salt thereof can be employed in accordance with the present invention. Any borate salt which is relatively soluble in the aqueous spinning solution can be suitably employed, as for example, the alkali metal borates such as sodium borate, potassium borate and the like. The solution is maintained weakly acidic, specifically between pH 3 and pH 5. The pH-of the solution can be regulated, if necessary, by addition of an acid thereto. Acids which can be added to the solution can be, for example, an inorganic acid such as sulfuric acid, nitric acid and hydrochloric acid; an organic acid such as acetic acid, tartaric acid, etc.; or a combination of an organic acid and a salt of an organic acid, e.g., citric acid and sodium citrate, acetic acid and sodium acetate, tartaric acid and potassium tartrate, tartaric acid and sodium citrate, etc.

When the spinning solution has a pH lower than 3, the rate of coagulation in the coagulating bath will be slower, and corrosion of the apparatus occurs due to the high acidity. On the other hand, when the pH is higher than 5, the solution becomes unstable causing an increase in viscosity thereby greatly damaging the spinning conditions.

The concentration of PVA in the spinning solution preferably ranges between 10 and 30 percent by weight; the degree of polymerization of the PVA is preferably more than 500. The spinning solution is spun into a strongly alkaline coagulating bath containing mainly water and sodium hydroxide or potassium hydroxide in a range of 10 to 100 g/l and sodium sulfate in a range of 100 to 330 g/l. Sodium hydroxide or potassium hydroxide concentrations of less than 10 g/l result in unfavorable effects such as reduction in the coagulating rate and reduction of drawability at the time of spinning. it is considered undesirable to exceed a sodium hydroxide or potassium hydroxide concentration of 100 g/l because gelling action due to alkali becomes so active, as to cause such properties as the yarn tenacity, yarn initial modulus and yarn creep to be more temperature dependent. When the concentration of sodium sulfate is less than 100 g/l, gelling action due to alkali overpowers the dehydration and coagulating action of the sodium sulfate. This causes swelling of the fiber at the time of coagulation, which advesely affects the quality of the product. 0n the other hand, concentrations of sodium sulfate exceeding 300 g/l cause de- In the present invention the PVA fiber thus spun is subjected to subsequent conventional treatments such as roller drawing, neutralization of alkali by the use of acid, wet-heat drawing, and is then water-rinsed to adjust the amount of boric acid remaining in the fiber to be in a range of 0.2 to 0.9 percent by weight of PVA. The residue of boric acid after water-rinsing should be more than 0.2 percent by weight of PVA because swelling of the fiber at the time of rinsing may occur when it is less than said amount. The swelling of the fiber will cause a slack in the fiber, which can then be caught in the rollers resulting in an unstable operation, thereby decreasing such properties as the yarn tenacity, yarn initial modulus and yarn creep.

These drawbacks are not observed in the present invention because the residue of boric acid present in the fiber may either react with PVA to effect formation of inter-or intramolecular cross-linkings, hang on the PVA chains, or remain unreacted. This is one of the characteristic features of the present invention. When the amount of said boric acid exceeds 0.9 percent by weight, the drawability of the fiber will decrease resulting in a decrease in the absolute values of the yarn tenacity and yarn initial modulus.

Thus, by selecting the optimum conditions for coagulation, theprocess can be stabilized for production of fibers having high drawability. Moreover, by so determining the conditions for waterrinsing as to maintain the residue of boric acid in a range of 0.2 to 0.9 weight percent, products having properties hardly dependent on temperature are obtained without reducing the dryheat drawability.

In the present invention, it is necessary to conduct the dry-heat drawing of the PVA fiber subsequent to water-rinsing, dehydration and drying, in order to achieve a total drawing ratio of more than 1300%. If the total drawing ratio is less than 1,300 percent, it is difficult to obtain PVA fiber exhibiting the abovementioned properties. According to this invention, the PVA fiber can be drawn to a total drawing ratio of 1,800 percent.

The properties of PVA fiber thus obtained are: yarn tenacity at 120C. of at least 7.5 g/d; yarn initial modulus at 120C. of at least g/d; and yarn creep at 135C. of less than 2 percent (elongation rate under the load of 1 g/d for 60 minutes). The fibers contain 0.2 to 0.9 percent of boric acid or a borate salt. The fibers of the present invention are superior to conventional PVA fibers containing no boric acid or borate with respect to high temperature properties.

The measurement of boric acid remaining in the synthetic fiber can be conducted in accordance with the following method:

A fiber weighing in terms of PVA approximately 2g is placed in a crucible, to which is added 0.1 mole]! aqueous sodium hydroxide solution to cover the fiber. After placing the crucible in a dryer at C. for one night, it is baked in an electric furnace at 400C. to 500C. for 60 minutes. The fiber in the crucible is then placed in a beaker, to which is added ion-exchanging water and maintained as it is for 60 minutes. A few drops of phenolphthalein indicator are added to the beaker. Whereupon, 0.1 mole/l hydrochloric acid is added until the color turns from red to yellow. After boiling for 30 to 60 minutes, it is cooled and neutralized to pH 7 by sodium hydroxide or hydrochloric acid addition as may be required. Mannite is added to the beaker and the solution is again neutralized to pH '7 by titrating with 0.1 mole/l sodium hydroxide. The volume (cc) being titrated is measured. The amount of boric acid remaining in the fiber is calculated by the following equation wherein W( g) is the weight of PVA in the test product measured in accordance with the method given above, and f and v(cc) are the strength and the titrated volume, respectively, of the 0.1 mole aqueous solution of sodium hydroxide:

The PVA synthetic fibers produced in accordance with the present invention exhibit excellent properties at high temperature. These properties are utilized to their fullest extent when the PVA fibers of the present invention are employed in a radial-ply or belted biasply tire.

In accommodating the ever increasing high-speed of automobiles in recent years, tires having improved qualities such as high speed performance and handling performance are rapidly coming into wide use. Illustrative of such tires are the radial-ply tire and the belted bias-ply tire.

The radial-ply tire comprises a carcass made of cord which is arranged in parallel to the sectional axis of the tire and a breaker providing a belt-like layer wherein the tire cord is arranged substantially in parallel with the circumference of the tire and on the outer side of the carcass to reinforce the tread. The radial-ply tire is very much different in its structure from that of the conventional bias-ply tire wherein cord woven into cord fabric is cut biased and provided in an angle of 40 to 60 against the circumferential direction of the carcass. The most peculiar characteristics in the radial-ply tire is the provision of the belt-like layer. Radial-ply tires having the above-mentioned characteristics will exhibit many performance advantages when the tire is built with the use of tire cord for the breaker which has properties more nearly corresponding to those of the carcass.

In the radial-ply tire of the present invention, cord is made of the PVA synthetic fiber described hereinabove containing boric acid or a borate salt in a range of 0.2 to 0.9 percent by weight of PVA and having yarn tenacity of at least 7.5 g/d at 120C., yarn initial modulus of at least 100 g/d at 120C. and yarn creep of less than 2 percent (under the load of 1 g/d for 60 minutes). The twist constant of the ply of said PVA yarn into the cord is 800 to 1,300. The cable twist (tums/lOcm) is conducted in a ratio of 80 to 100 percent of the ply twist (turns/ cm).

The principle qualifications of the material for the tire cord to be used in the breaker are therefore that it has high tenacity and high modulus, and PVA synthetic fibers are generally known to have high tenacity and high modulus. However, conventional PVA fibers are defective in that they exhibit a remarkable drop in tenacity and modulus when the temperature rises, as do other thermoplastic synthetic fibers such as polyesters and polyamides. Moreover, the inside of a tire when in use is normally in a state of high temperature, aproximately 100C., because of the heat buildup caused by the running of the tire. Of necessity, this also occurs in the radial-ply tire. Thus, the tire cord for the breaker is also affected by said temperature increase. A breaker made from conventional PVA fibers whose properties at high temperature are highly dependent on the temperature will not act as a strong and non-extensible breaker checking the deformation of a radial-ply tire. Of course, it is not altogether impossible to supplement this lack of strength and modulus in the conventional PVA fiber by increasing the amount of fiber used in a tire. However, this creates a great problem in that the durability of the tire is greatly reduced because the heat buildup becomes greater as the amount of fiber used increases, thereby decreasing adhesion and fatigueresistance.

In view of the above, the present invention provides a radial-ply tire utilizing the PVA fibers of the present invention which have excellent properties at high temperature. It has been found herein that a radial-ply tire will not be able to exhibit its advantages unless the PVA fiber to be used contains boric acid or a borate salt in an amount of from 0.2 to 0.9 percent by weight and exhibits a yarn tenacity of at least 7.5 g/d at 120C., yarn initial modulus of at least g/d at C. and yarn creep of less than 2 percent at C. This fact remains valid regardless of the conditions employed in the construction of the cord, the heat-treatment of the cord or structure of the tire.

One of the factors which should be taken into consideration is the construction of the cord. The number of twists exerts a significant influence on the performance of the final product. There is no inclusive number of twists suitable for any material. It is inseparably intertwined with the properties of the material. It is, therefore, impossible to apply the suitable number of twists for the conventional PVA fiber or other fibers to the PVA fiber of the present invention. Repeated tests have been made by actually running tires containing the PVA fibers of the present invention in varying numbers of twists to determine the optimum twisting for the cord of the breaker.

As complicated as it is, the properties of a tire are both in direct and in inverse proportion to the number of twists. For instance, the fatigue-resistance improves in direct proportion to the increase in the number of twists, whereas properties relating to the modulus such as rolling resistance, cornering characteristics and tread wear-resistance are inversely proportional.

It is necessary for any kind of tire, not the radial-ply tire along, to satisfy the diverse qualifications required thereof. The results of the tests mentioned above have shown that the PVA synthetic fibers of the present invention are limited with respect to the number of twists required to make the cord of the breaker in the radialply tire, i.e., the twist constant of the ply, can range from 800 to 1,300, and the cable twist (tums/ 10cm) can range from 80 to 100 percent of the ply twist (tums/ 10cm). The term twist constant" used in the present invention denotes K in the following equation wherein D is denier and T is the number of twists (number/lOcm):

K \l D X T The number of twists increases proportionately with the increase in the value K.

When the twist constant of the ply is less than 800, not only does the shape of the cord become very uneven and the performance of the tire decreases, but

s also the fatigue-resistance of the cord becomes insufficreases when the cable twist (turns/10cm) is less than D. Tread Wear-Resistance An automobile with tires whose air pressure is ad- 80 percent of the ply twist (turns/10cm).

On the other hand, when the twist constant of the ply exceeds 1,300, the properties of the PVA fiber such as high tenacity and high modulus are lost, thereby losing the advantages of the radial-ply tire in rolling resistance, tread wear-resistance and cornering characteristics. It is also considered undesirable for the cable twist (turns/10cm) to exceed the limit specified above, i.e., 100 percent of the ply twist (turns/10cm), because it not only reduces the tenacity and modulus of the cord by a remarkable degree but also causes kinking of the cord under relaxation and handling difficulties.

The tire cord is normally subjected to a dipping treatment in order to give it adhesion to rubber. The adhesive employed in the present invention is not limited to specific types, but any known adhesive suitably used in the rubber industry can be used, the most preferred being RFL (mixture of an alkaline initial condensate of resorcinol and formalin with latex), or that used concurrently with a latex containing polyvinyl pyridine. The conditions for the dipping treatment may be such as those employed in the method used for treatment of the cordof conventional bias-ply tires. The drying, baking, stretching and heat-treatment are conducted at a temperature above 200C.

In carrying out the present invention, any material that is used in the ordinary bias-ply tire may be used in the carcass.

The present invention is also applicable to the manufacture of belted bias-ply tires which are provided with a blet-like layer of tire cord being substantially in parallel with the circumference of the tire and located on the outside of the carcass to reinforce the tread, like the one in the radial-ply tire, but whose carcass is of the same structure as that of the ordinary bias-ply tire.

The following examples further illustrate the present invention. Unless otherwise stated, all percentages and parts are by weight.

The various tests conducted upon the radial-ply tires and belted bias-ply tires prepared in accordance with the present invention are identified and described below.

A. Plunger Test The result is evalated in terms of the energy (kg.cm) expended before the tire breaks due to a plunger slowly penetrating the tire. The inner pressure of the tire here is 2.7 kg/cm. The greater the value is, the stronger the tire is.

B. High Speed Test According to MVSS No. 109 (ASTM), a tire whose air pressure is adjusted to be 1.7 kg/cm is started running at 80 km/hr. on a testing drum. The speed is gradually increased in the case of no defects in the tire after running a predetermined hour. The result is evaluated by the maximum speed (km/hr.) at the breakage of the tire and running time (minutes) at the same speed. The larger the numerical value, the greater its high speed endurance is.

C. Cornering Power The cornering force (kg) of a tire whose air pressure is adjusted to be 1.7 kg/cm is measured at a speed of 30 km/hr., load of 125 kg and slipping angle of 10. The value obtained by dividing said cornering force by the slipping angle denotes the cornering power (kg/deg). The greater the value is, the better the cornering characteristic is.

justed to 1.7 kg/cm is run on a test course.

After running 20,000 km at a speed of approximately to km/hr., the amount of abrasion of the tread which touches the ground is measured. The tread wearresistance is expressed in the distance the tire runs while the tread is abraded 1mm. The greater the value is, the greater the wear-resistance of the tread is.

E. Durability An automobile with tires whose air pressure is adjusted to 1.7 kg/cm is run on a test course for 20,000km at a speed of about 80 to 100 km/hr. Sampling the tire cord of the breaker before and after the test-run, the strength of the cord is measured. It is expressed interms of residual strength (percent) of the cord of the tires tested as against the original cord. The higher the value is, the greater the durability is.

EXAMPLE 1 10kg of an aqueous spinning solution containing 1.7kg of PVA with a degree of polymerization of 1,750 and degree of saponification of 99.5 mole percent, and 34g of boric acid and a sufficient amount of nitric acid to adjust the pH to 4.3 is prepared. The spinning solution is passed through spinning nozzles comprising 600 spinning holes, 008mm in diameter into a coagulating bath containing 30 g/l of sodium hydroxide and 230 g/l of sodium sulfate. The fiber thus spun is then taken out of the bath at a rate of 10 m/min., and then subjected to subsequent treatments such as; roller drawing of 100 percent; neutralization in a bath comprising 70 g/l of sulfuric acid and 300 g/l of sodium sulfate; wet-heat drawing of 150 percent; water-rinsing to adjust the amount of boric acid to be 0.45 percent; dehydration and drying; and dry-heat drawing of 220 percent. The final product obtained is drawn to a total drawing ratio of 1,500 percent.

The product thus obtained exhibits a yarn tenacity of 9.3 g/d at C., yarn initial modulus of g/d at 120C. and yarn creep of 1.4 percent at 135C.

In manufacturing radial-ply tires for passenger cars having the size of 13 with the use of the PVA synthetic fibers of the present invention, PVA fibers of 1,200 d/600F (f is the number of filaments) are employed for the breaker, while high tenacity rayon super 2 1,650 d/l,l00f is employed for the carcass. Both yarns are twisted and woven into cord fabric, whose specifications are given in Table 1.

TABLE l-Continued gs Tal gg fgs g 2) itotal drawing ratio of 1,500 percent is obtained in the Cord Density (ends/cm) 49 5 same manner as in Example 1, except that sodium bofabric 32 rate 18 employed in an amount of 1.5 percent of PVA A .7 a a it a in lieu of boric acid and tartaric acid is employed in lieu Both cord fabrics A and B are subjected to normal dipof nitric acid for adjustment of pH. The product obping with the use of RFL solution. The cord fabric A tained exhibiting a yarn tenacity of 9.1 g/d at 120C., is then dry-heat treated for 3 minutes at 200C., while. yarn initial modulus of 127 g/d at 120C. and yarn the cord is stretched 2.5 percent. On the other hand, creep of 1.5 percent at 135C. the cord fabric B is dried at 150C. while maintaining Radial-ply tires were manufactured using yarn as preit original length, pared above; however, the twist of the cord for the bre- The tire of the present invention is obtained with the aker was varied as shown below in Table 3 and the peruse of the above specified cord fabrics in the breaker l 5 formance Of the resulting tires was compared. and carcass, respectively, using conventional tire buildamples are presented for radial-ply tires which are ing processes as rubber tgpping, tire forming, vulcaniidentical to the tire Of the present invention in structure ti d p i fl ti and size, but which use PVA fiber in the breaker that However, the tire was constructed with 4 plys in the does not fulfill various of the manufacturing conditions breaker and 2 plys in the carcass. and property requirements of the present invention.

The results of various tests on the performance of the The results of the tests on the comparative examples tireare given in Table 2. In the Table, comparative exarealso given in the Table,

TABLE 2 Example Comparison Comparison Comparison Comparison Comparison Comparison Compgrison i e .7. e i I EXAMPLE 2 PVA fiber containing sodium borate and drawn to a Material.

Polymerization degree of PVA 1,750 1,750 1,750 1,750 1,750 1,750 1,750 1,750 Saponification degree of PVA 99.5 99.5 99.5 99.5 99.5 99.5 99.5 99.5

(mol '7!) Manufacturing Conditions Spinning solution:

the concentration of PVA (7( 17 17 17 17 17 18 18 17 the amount of boric acid added 2.0 2.2 2.2 2.2 2.2 2.6 2.6 2.0

pH 4.3 4.1 4.1 4.1 4.1 4.0 4.0 4.3 Coagulation bath:

NaOH (g/l) 8 110 80 15 40 30 Na.,SO, (g/l) 230 260 150 90 360 220 220 230 Neutralization bath:

H 80 (g/l) 70 70 incapable of 70 80 70 being spun Na,SO (g/l) 300 300 300 300 320 320 300 Drawing:

total drawing ratio (71) 1,500 1,100 1,200 1,000 1,500 1,200 1,100 roller drawing ('7!) 100 100 100 100 100 100 wet-heat drawing (71) 150 150 140 150 150 140 150 dry-heat drawing (71) 220 140 192 220 192 140 Yarn Properties 1 Amount of residue of boric acid 0.45 0.51 0.52 0.49 0.15 1.00 0.46

("/1 Tenacity (120C.) (g/d) 9.3 6.2 710 5.4 7.3 7.0 6.5 Initial modulus( 120C.) (g/d) 72 82 63 91 82 96 Creep (135C) (7:) 1.4 2.5 2.2 3.1 2.3 2.4 2.3 Tire Performance Plunger test (kg.cm) 5863 3524 4175 2643 4632 4298 3485 High speed test [(km/hr).min] 217,20 184,10 192,25 160,40 208,23 184,24 192,20

Cornering power (kg/deg.) 40.5 31.9 32.8 30.2 30.7 32.5 33.4 Tread wear-resistance (kg/mm) 8920 7710 8290 7630 8030 7960 8140 Durability ('4) 95 73 76 70 86 82 89 Note to Table 2:

ln Example 1 l0 comparative Example 4, nitric acid is used to adjust pH. 1. tartaric acid used to adjust pH 2v acetic acid and sodium acetate used to adjust pH 3v sample exhibited poor drawability 4. sample exhibited poor spinahility VA 7 TABLE 3 Example 2 Comparison 8 Comparison 9 Comparison 10 Comparison 11 number of twist ply 30 30 23 18 4O (turns/10cm) cable(turns/l0em) 30 20 1 1.5 18 40 direction of twist ply Z Z Z Z Z cable S S S S S twist constant of 1,039 1,039 797 624 1,386

TABLE 3 -Continued ExampleZ Comparison 8 Comparison 9 Comparison 10 Comparison ll are twistlply m it? "W *4 6i 56 1 100 twist X100(%) no trouble after break in cord of break in cord of break in cord of no trouble after running 40,000 breaker after breaker after breaker after running 40.000

km I running 30,000 running 24.000 running 12.000 km km km km, durah|l|ty(% 97 81 73 V 96 V residual strength of cord after running 20,000 km) cornering power 40.3 39.6 43.3 45.6 30.6 (kg/deg.)

EXAMPLE 3 15 are taken out of the bath at a rate of m/min. The

An aqueous PVA solution having a concentration of PVA of weight percent and containing 150g of PVA with a degree of polymerization of 2,350 and a degree of saponification of 99.5 mole percent is admixed with 30g of boric acid (2 percent by weight of PVA) and HI small amount of acetic acid to prepare a spinning solution of pH of 4.5. The spinning solution is spun into a strongly alkaline coagulating bath mainly of water con-' taining 40 g/l of sodium hydroxide and 250 g/l of sodium sulfate. After taking the spun fibers out of the bath at a rate of 10 m/min., they are subjected to roller drawing of 100%, neutralization, wet-heat drawing of 150 percent, water-rinsing to adjust the amount of boric acid residue to 0.4 percent by weight of PVA, dehydration and drying, and dry-heat drawing of 200 percent. The product (1,200d/600f) is thus drawn to a total drawing ratio of 1,400 percent. The product thus obtained exhibits a yarn tenacity of 9.2 g/d at 120C, yarn initial modulus of 131 g/d at 120C, and yarn creep of 1.9 percent at 135C; the product is superior in its properties at high temperature.

This yarn thus obtained is used to construct the breaker of a radial-ply tire by twisting it into a cord (1,200d/l/3) under the following conditions:

ply twist 30 turns/10cm cable twist v 30 turns/10cm direction of twist ply Z cable S twist constant of ply 1,039

cable twist/ply twist 100 No difficulties are observed after running 35,000km. The durability is 98 percent and the cornering power is 40.8 kg/deg.

EXAMPLE 4 The spinning solution is passed through nozzles of 1,000 holes in number and 0.1Smm in diameter into the coagulating bath containing 50 g/l of sodium hydroxide and 200 g/l of sodium sulfate. Then, the fibers spinning condition is very stable in this case; during two weeks spinning, no difficulties such as clogging of the nozzles is observed. The fiber thus spun is then subjected to the same processing as in Example 3; i.e., r01- ler drawing, neutralization, wet-heat drawing, waterrinsing to adjust the amount of residual boric acid to 0.5 percent by weight of PVA, dehydration, drying, and dry-heat drawing. The product (1,800d/1,000f) thus obtained is drawn to a total drawing ratio of 1,400 percent. The product exhibits a yarn tenacity of 9.3 g/d at 120C, yarn initial modulus of 134 g/d at 120C, and yarn creep of 1.8 percent at 135C.

The yarn thus obtained is used to construct the breaker of a radial-ply tire by twisting it into a cord (1,800d/l/2) under the following conditions:

My twist om Lme cable twist 30 turns/10cm direction of twist ply Z cable S twist constant of ply 1,272 40 cable twist/ply twist x00 No difficulties are observed after running 35,000 km. The durability is 96 percent and the cornering power is 41.2 kg/deg.

EXAMPLE 5 TABLE 4 BREAKER (Belt) .Cmdsamtt stion, emu: Number of twist ply tturnsi 10cm) 39 cableitums/lOem) 30 Twist constant ct ply 12 12 Cable twist] 1y twist X(%) 100 Direction 0 twist ply twist 2 cable Density of cord (ends/cm) 30 Ply of breaker (ply) 2 CARCASS 2 ply polyester cords TIRE PERFORMANCE 5 Plunger test (kg.cm) 5685 High speed test [(km/hr), min] 192,10 Cornering Power (kg/deg.) 38 Tread wear-resistance (kg/mm) 6810 Durability (breaker cord) 92 EXAMPLE 6 Belted bias-ply tires for passenger cars of the size described in Example 5 are prepared using PVA fibers of l200d/600f obtained in the manner described in Examl5 ple 1 for the breaker (belt) and rayon super 2 for the carcass. Both yarns are twisted and woven into cord fabric, whose specifications and the results of various tests on the performance of the tire are given in Table 5 o TABLE 5 BREAKER (Belt) Cord construction l200d/l/3 Number of twist ply( turns/ 10cm) 30 cable(turnsl 10cm) 25 Twist constant of ply 1039 Cable twist/ply twist x100 83 Direction of twist ply twist Z cable S twist Density of cord (ends/5cm) 30 Ply of breaker (ply) 2 CARCASS 2 ply rayon cords Tire performance ,7 2....

Plunger test (kg-cm) 5739 High speed test [(km/hr), min] [92,16 Cornering Power (kg/deg.) 36.5 Tread wear-resistance (kg/mm) 6540 Durability (breaker cord) 94 The PVA synthetic fibers of the present invention which exhibit outstanding properties at high temperature find widespread application, for example, they can be employed in the tension member of V belts and for reinforcement of hoses. The high modulus and loww u s lai nedisa... A

1. Tire cord comprising polyvinyl alcohol fibers containing boric acid or a water soluble borate salt thereof in an amount of from 0.2 to 0.9 percent by weight of polyvinyl alcohol, said fibers having been drawn a total of more than about 1,300 percent and exhibiting the following high temperature properties:

Yarn Tenacity at 120C Yarn Initial Modulus at 120C Yarn Creep at 135C at least 7.5 gms/denier at least 100 gms/denier less than 2% twisted under a twist constant of ply of 800 1,300 in a cable twist (turns/10cm) of percent of the l stwi t ($F FP. QEE);....

2. A radial-ply tire whose breaker is comprised of corqese lnes in 3. A belted bias-ply tire whose breaker is comprised 99Id2 s1 nd., n.1ain1. W

UNITED STATES PATENT OFFICE g 5 CERTIFICATE OF CORRECTION Patent No. 3,826,298 Dated July 50, 197

Inventor(s) Shoichi Tanaka et a1.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column 10, Example 2 should read as follows:

PVA fiber containing sodium borate and drawn to a total drawing ratio of 1,500 percent is obtained, in the same manner as in Example 1, except that sodium borate is employed in an amount of 1.5 percent of PVA in lieu of boric acid and tartaric acid is employed-in lieu of nitric acid for adjustment of pH. The product o'ptained exhibiting a yarn tenacity of 9.1 girl at l20C.,

. yam initial modulus of 127 gld at XZOC. and yarn creep of 1.5 percent at 135C.

. Radial-ply tires were manufactured using yam as pre- 7 pared above; however, the twist of the cord for the bre aker was varied as shown below in Table 3 and the performance of the resulting tires was compared.

In column 11 and 12, Table B-continued should be IABLE 3-Continued Example 2 Comparison 8 Comparison 9 Comearii'oa i0 Comearisnn l I cable hbiflffii '1. u. h fi I 6"] n i i ROD I mg 232: ino trouble after break in cord of break in cord of break in cord of no trouble after T running 40.000 breaker after breaker after breaker a'rer running: 40,090

km running 30.000 running 24.000 running 12.030 km I 1 32552,; m 9 7 5/ 7 3 a. 7.; I 5:33; 1 -3 3% yrs as; 0.4

Signed and sealed this 22nd day of April 1975.

( SEAL) Attest C MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks USCOMM-DC 60376-P89 v.5. GOVERNMENT PRINTING orncz: 93o 

2. A radial-ply tire whose breaker is comprised of cord as defined in claim
 1. 3. A belted bias-ply tire whose breaker is comprised of cord as defined in claim
 1. 